Implantable orthopedic device component selection instrument and methods

ABSTRACT

The present invention provides tools and methods designed to aid in the placement of artificial facet joints at virtually all spinal levels. One aspect of the present invention is a measurement tool for installing an artificial cephalad facet joint including a fixation measurement element and a support arm element. This measurement tool assists in the selection and/or configuration of an artificial cephalad facet joint for implantation in a patient. Another aspect is a measurement tool for installing a caudad facet joint including a stem element and a trial caudad bearing surface element. This measurement tool assists in the selection and/or configuration of a caudad facet joint for implantation in a patient. Yet another aspect is a measurement tool holder including a measurement surface connected to a holder element. This tool holder assists in determining the measurements obtained with the caudad facet joint measurement tool.

CROSS-REFERENCE

This application is a continuation-in-part of commonly assigned U.S.patent application Ser. No. 10/831,651 to Augostino et al. filed Apr.22, 2004, now U.S. Pat. No. 7,051,451 and entitled “Facet jointMeasurement and Implant Tools,” which is incorperated herein byreference.

This application is also a continuation-in-part of commonly assignedU.S. patent application Ser. No. 11/071,541 to Kuiper et al., filed Mar.2, 2005, and entitled “Crossbar Spinal Prosthesis Having a ModularDesign and Related Implantation Methods,” which is incorporated hereinby reference which in turn claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/642,321 to Funk et al, filed Jan. 7, 2005, andentitled “Component Selection Instrument”, which is also incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to implantable spinal devices, systems, andmethods for treating various types of spinal pathologies. The inventionrelates in particular to the sizing and attachment of implantabledevices to spinal vertebrae using component selection tools and methods.

BACKGROUND OF THE INVENTION

Back pain, particularly in the small of the back, or lumbosacral region(L4-S1) of the spine, is a common ailment. In many cases, the painseverely limits a person's functional ability and quality of life. Backpain interferes with work, routine daily activities, and recreation. Itis estimated that Americans spend $50 billion each year on low back painalone. It is the most common cause of job-related disability and aleading contributor to missed work.

Through disease or injury, the laminae, spinous process, articularprocesses, facets and/or facet capsule(s) of one or more vertebralbodies along with one or more intervertebral discs can become damagedwhich can result in a loss of proper alignment or loss of properarticulation of the vertebra. This damage can result in anatomicalchanges, loss of mobility, and pain or discomfort. For example, thevertebral facet joints can be damaged by traumatic injury or as a resultof disease. Diseases damaging the spine and/or facets includeosteoarthritis where the cartilage of joint is gradually worn away andthe adjacent bone is remodeled, ankylosing spondylolysis (or rheumatoidarthritis) of the spine which can lead to spinal rigidity, anddegenerative spondylolisthesis which results in a forward displacementof the lumbar vertebra on the sacrum. Damage to facet joints of thevertebral body often can also results in pressure on nerves, commonlyreferred to as “pinched” nerves, or nerve compression or impingement.The result is pain, misaligned anatomy, and a corresponding loss ofmobility. Pressure on nerves can also occur without facet jointpathology, e.g., a herniated disc.

One conventional treatment of facet joint pathology is spinestabilization, also known as intervertebral stabilization.Intervertebral stabilization desirably controls, prevents or limitsrelative motion between the vertebrae, through the use of spinalhardware, removal of some or all of the intervertebral disc, fixation ofthe facet joints, bone graft/osteo-inductive/osteo-conductive material(with or without concurrent insertion of fusion cages) positionedbetween the vertebral bodies, and/or some combination thereof, resultingin the fixation of (or limiting the motion of) any number of adjacentvertebrae to stabilize and prevent/limit/control relative movementbetween those treated vertebrae. Stabilization of vertebral bodies canrange from the insertion of motion limiting devices (such asintervertebral spacers, artificial ligaments and/or dynamicstabilization devices), through devices promoting arthrodesis (rod andscrew systems, cable fixation systems, fusion cages, etc.), up to andincluding complete removal of some or all of a vertebral body from thespinal column (which may be due to extensive bone damage and/or tumorousgrowth inside the bone) and insertion of a vertebral body replacement(generally anchored into the adjacent upper and lower vertebral bodies).Various devices are known for fixing the spine and/or sacral boneadjacent the vertebra, as well as attaching devices used for fixation,including: U.S. Pat. Nos. 6,811,567, 6,619,091, 6,290,703, 5,782,833,5,738,585, 6,547,790, 6,638,321, 6,520,963, 6,074,391, 5,569,247,5,891,145, 6,090,111, 6,451,021, 5,683,392, 5,863,293, 5,964,760,6,010,503, 6,019,759, 6,540,749, 6,077,262, 6,248,105, 6,524,315,5,797,911, 5,879,350, 5,885,285, 5,643,263, 6,565,565, 5,725,527,6,471,705, 6,554,843, 5,575,792, 5,688,274, 5,690,630, 6,022,350,4,805,602, 5,474,555, 4,611,581, 5,129,900, 5,741,255, 6,132,430; andU.S. Patent Publication No. 2002/0120272.

SUMMARY OF THE INVENTION

What is needed are methods and tools for facilitating the sizing,orientation and implant of implantable spinal devices such as artificialfacet joints. Moreover, there is a need in the art for methods anddevices which facilitate the less-invasive, minimally-invasive and/ornon-invasive measurement of the anatomical characteristics (includingsize, shape, orientation and/or relationship) of anatomical features ofbones such as the vertebrae. The present invention provides tools andmethods designed to aid in the placement of implantable facet joints atvirtually all spinal levels including, but not limited to, L1-L2, L2-L3,L3-L4, L4-L5, L5-S1, T11-T12, and T12-L1.

Because the specific features of a patient's spinal anatomy can varysignificantly from patient to patient (and can also vary within thevarious spinal levels of an individual patient or even vary between thefacet joints in a single vertebral level), an implantable spinal devicesuitable for implantation into a patient will desirably be configured ortailored to be patient specific in order to accommodate the specificfeatures of that patient's spinal anatomy. For example, the size,spacing and orientation of the pedicles, lamina and associated spinalanatomy, as well as the size, spacing and orientation of the individualfacet joints to be replaced, can vary widely depending upon the leveland/or patient to be treated.

In order to accommodate such variations in anatomy, a configurableand/or modular implantable device system (comprising multipleconfigurable and/or interchangeable components of varying shapes and/orsizes) may be used to tailor the implantable device to the varyinganatomical demands of a given patient. Once the surgical site has beenprepared, the implantable device can be assembled and/or configured fromcomponents chosen by the physician based on anatomical measurements ofthe treatment site during the surgery. The disclosed invention desirablyfacilitates such measurements of the treated anatomy.

In one aspect, the present invention provides a measurement tool forconfiguring and installing a cephalad facet joint implantable deviceincluding a fixation measurement element and a support arm element. Thismeasurement tool assists in the selection of a cephalad facet jointimplantable device for implantation in a patient. The measurement toolcan be used in the determination of the dimensions of a cephalad facetjoint implantable device. Particularly, this measurement tool can beused to determine the length of the fixation element and support armelement of the cephalad facet joint implantable device.

In some embodiments, the connection between the fixation measurementelement and support arm element is a polyaxially adjustable connection.In one embodiment, the fixation measurement element has indentationswhich control the vertical movement of the support arm element. Theindentations on the fixation measurement element can also permit thedetermination of the length of the fixation element of a cephalad facetjoint implantable device.

In one embodiment, the support arm element supports a trial facet jointbearing surface. The bearing surface is intended to predict the locationof the facet joint bearing surface of an actual implantable deviceintended for implantation in a patient.

The fixation measurement element in one embodiment is adapted andconfigured to permit measurements for determination of the length of thefixation element of a cephalad facet joint implantable device forimplantation in a patient. In another embodiment, the fixationmeasurement element includes markings to assist in the determination ofthe length of the fixation element of a cephalad facet joint implantabledevice.

In another aspect, the present invention provides a caudad facet jointimplantable device measurement system including a stem element and atrial caudad bearing surface element connected to each other by afastener or fastening mechanism. This measurement tool assists in theselection of a caudad facet joint implantable device for implantation ina patient. The measurement tool can be used in the determination of thedimensions of a caudad facet joint implantable device. Particularly,this measurement tool can be used to determine the length of thefixation element of the caudad facet joint implantable device to beimplanted in a patient. Also, this tool can be used to determine theangle between the artificial facet joint element and fixation element ofthe caudad facet joint implantable device. If desired, the mechanism canpermit motion between the elements for alignment purposes and also allowlocking of the chosen configuration/orientation once determined.

In one embodiment, the fastener used in the caudad facet jointimplantable device measurement tool is a screw. Examples of othersuitable fasteners could include stems, posts, threads, polyaxialmechanisms, splines, tapers, press fits, bayonet, cap screws, balldetents, friction fits, cams, collets and/or clamps. In certainembodiments, the fastener permits vertical movement of the trial caudadbearing surface element along the stem element. In other embodiments,the fastener permits rotation of the trial caudad bearing surfaceelement in different planes with respect to the stem element. Theseplanes can include movement along the axial and median planes.

In another embodiment, the stem element is adapted and configured topermit measurement of the length of a fixation element of a caudad facetjoint implantable device to be implanted in a patient. In yet anotherembodiment, the stem element of the measurement tool includes markingsto permit the measurement of the length of the fixation element.

In one of the embodiments, the measurement tool for the caudad facetjoint implantable device is adapted and configured to permit measurementof the angle between the artificial facet joint element and fixationelement of a caudad facet joint implantable device to be implanted in apatient. The angle measurements can include measurements in the median,horizontal and frontal planes (such measurements could also includemeasurements relative to the coronal, sagittal and/or axial planes, ifdesired). In one embodiment, to facilitate the determination of theangle measurement, the trial caudad bearing surface element is adaptedand configured to interact with a measurement tool holder.

In one aspect, the invention is a measurement tool holder including ameasurement surface connected to a holder element. This tool holderassists in determining the angle measurements obtained with the caudadfacet joint. implantable device measurement tool. The caudad facet jointimplantable device measurement tool can be placed in the tool holder andthe angle between the artificial facet joint element and fixationelement of a caudad facet joint implantable device can be determined.

In one embodiment, the measurement tool holder is adapted and configuredto hold the measurement tool for the caudad facet joint implantabledevice. In yet another embodiment, the measurement surface of the toolholder includes two plates at right angles to each other. The plates caninclude markings to permit determination of the angle measurements,preferably in the horizontal and median planes.

Another aspect of the invention provides a method for determining thedimensions of a cephalad facet joint implantable device to be implantedin a patient. The method includes the steps of forming a hole at alocation in the vertebra and placing a fixation measurement element of acephalad facet joint implantable device measurement tool into the hole.Further optional steps include the steps of obtaining a first lengthmeasurement to determine length of a fixation element of a cephaladfacet joint implantable device to be implanted in a patient; andobtaining a second length measurement for determining the length of asupport arm element of the cephalad facet joint implantable device. Invarious embodiment, the measurement tool can be used in conjunction witha caudad implantable device or other implanted device, or can be used inconjunction with the caudad joint surface or other natural anatomicallandmark.

Yet another aspect of the invention provides a method for determiningthe dimensions of a caudad facet joint implantable device to beimplanted in a patient. The method includes the steps of forming a holeat a location in the vertebra and placing a caudad facet jointimplantable device measurement tool into the hole. Further optionalsteps include the steps of obtaining a length measurement whichindicates the length of a fixation element of a caudad facet jointimplantable device to be implanted in a patient; and obtaining an anglemeasurement which indicates the angle between an artificial facet jointelement and a fixation element of the caudad facet joint implantabledevice. In an alternate embodiment, the external surfaces of themeasurement tool could incorporate calibrated markings allowing anglemeasurements to be determined without an associated measurement fixture.

In yet another aspect of the invention a component selection instrumentis provided that facilitates the less-invasive, minimally-invasiveand/or non-invasive measurement of the anatomical characteristics of thedrill channel created in the pedicle in anticipation of implantation ofa facet joint implantable device. In the various embodiments, thecomponents of the component selection instrument can be visualized usingnon-invasive visualization (such as fluoroscopy, etc.) to determine thevarious appropriate components of a modular facet replacement systemwithout requiring actual trialing of the components prior to permanentimplantation.

The invention also includes a component selection tool adapted andconfigured for use in a spinal column comprising: a stem; a head; and afirst marker having a first two dimensional geometric profile at a firstlocation within the component selection tool and a second marker havinga second two-dimensional geometric profile at a second location withinthe component selection tool. In some embodiments, the stem and head ofthe component selection tool are integrally formed. In otherembodiments, the stem and head are component parts and the stem isadapted and configured to engage the head. In yet other embodiments, atleast one of the stem and the head are formed from radiolucent material.The first marker can be configured as a radiopaque ball. In contrast,the second radiopaque marker can be configured as a cylindrical rod ortube with a shaped exterior surface. Suitable exterior shapes for therod include smooth, turned, notched, and etched. Moreover, in otherembodiments, a plurality of second radiopaque markers can be provided toprovide additional reference markings. In embodiments where a pluralityof second radiopaque markers are used, each of the markers can have thesame or different shapes which are selected from smooth, turned andnotched. In at least some embodiments, the plurality of secondradiopaque markers can be configured to lie within a single plane withinthe component selection tool and can further be configured to beparallel one another within the plane. In at least some embodiments, thesecond radiopaque marker(s) are located within the head of the componentselection tool. Other embodiments of the invention can be configured toprovide a third radiopaque marker. The third radiopaque marker can bepositioned in a plane that is perpendicular to the plane in which thesecond radiopaque markers lie. As with the second radiopaque markers,more than one third radiopaque marker can be provided, each or any ofwhich can have an exterior shape that is smooth, turned or notched.Additionally, the third radiopaque marker(s) can be positioned withinthe head of the component selection tool. Where second and thirdradiopaque markers are used, the second markers can be configured with afirst exterior shape and the third markers can be configured with asecond exterior shape to assist in assessing the position of thecomponent selection instrument relative to the anatomy. The thirdradiopaque markers can also lie parallel one another within the plane orbe positioned non-parallel. The stem of the component selection tool canbe configured to be telescoping, and can be configured to have a firstdiameter at a distal end and a second diameter at a proximal end. Thefirst radiopaque marker can be positioned within the stem eitherintegrally or located within a hollow shaft of the stem

The invention also includes a pair of component selection tools adaptedand configured for use in a right and left side of a vertebral body of aspinal column or a first and second vertebral body, each componentselection tool comprising: a stem; a head; and a first marker having afirst two dimensional geometric profile at a first location within thecomponent selection tool and a second marker having a secondtwo-dimensional geometric profile at a second location within thecomponent selection tool wherein the second marker in a first componentselection tool has a first shape and the second marker in a secondcomponent selection tool has a second shape different than the firstshape of the first component selector tool markers. In some embodimentsthe shape of the first and second, second radiopaque markers can havethe same or different shapes which are selected from smooth, turned,notched and etched. In some embodiments, the stem and head of thecomponent selection tool are integrally formed. In other embodiments,the stem and head are component parts and the stem is adapted andconfigured to engage the head. In yet other embodiments, at least one ofthe stem and the head are formed from radiolucent material. In at leastsome embodiments, the plurality of second radiopaque markers of eitherof the first or second component selection tool can be configured to liewithin a single plane within the component selection tool and canfurther be configured to be parallel one another within the plane. In atleast some embodiments, the second radiopaque marker(s) of either of thefirst or second component selection tools are located within the head ofthe component selection tool. Other embodiments of the invention can beconfigured to provide a third radiopaque marker. The third radiopaquemarker for each of the component selection instruments can be positionedin a plane that is perpendicular to the plane in which the secondradiopaque markers lie. As with the second radiopaque markers, more thanone third radiopaque marker can be provided, each or any of which canhave an exterior shape that is smooth, turned or notched. Additionally,the third radiopaque marker(s) can be positioned within the head of thecomponent selection tool. The third radiopaque markers can also lieparallel one another within the plane or be positioned non-parallel. Thestem of the component selection tool can be configured to betelescoping, and can be configured to have a first diameter at a distalend and a second diameter at a proximal end. The first radiopaque markercan be positioned within the stem either integrally or located within ahollow shaft of the stem.

Embodiments of the invention also include methods of using a componentselection tool comprising: accessing a target anatomy; creating a pilothole within a portion of the target anatomy; inserting a stem of acomponent selection tool within the pilot hole; taking a first image ofthe target anatomy having the component selection tool; analyzing theimage of the target anatomy with the component selection tool todetermine position of a first marker and a second marker; and selectinga component for implantation into the target anatomy. Templates can beused in combination with the image to analyze the image of the targetanatomy with the component selection tool. Further, the pilot hole canbe revised to achieve a larger diameter. Thereafter the componentselection tool can be placed within the revised pilot hole before takinga second image of the component selection tool in the revised pilothole.

Embodiments of the invention also include the use of kits, such as a kitcomprising a first component selection instrument having a first markerand at least one second marker and a second component selectioninstrument having a first marker and at least one second marker, whereinthe geometric profile of the second marker in the first componentselection instrument is not the same as the geometric profile of thesecond marker in the second component selection instrument.

Embodiments of the invention also include methods, such as a method ofusing a component selection tool comprising: accessing a target anatomy;creating a pilot hole within a portion of the target anatomy; insertinga stem of a component selection tool within the pilot hole; taking afirst image of the target anatomy having the component selection tool;analyzing the image of the target anatomy with the component selectiontool to determine position of a first marker and a second marker; andselecting a component for implantation into the target anatomy.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a lateral view of a normal human spinal column;

FIG. 2 is a superior view of a normal human lumbar vertebra;

FIG. 3 is a lateral view of a functional spinal unit;

FIG. 4 is a postero-lateral oblique view of a vertebrae;

FIG. 5 is a perspective view of the anatomical planes of the human body;

FIG. 6 is a perspective view of a cephalad facet joint implantabledevice suitable for replacing the inferior half of a natural facet jointon a superior vertebral body;

FIG. 7A-B are views of one embodiment of a measurement tool forinstalling a cephalad facet joint;

FIGS. 8A, 8B and 8C are views of one embodiment of an installedmeasurement tool for an artificial cephalad facet joint;

FIG. 9 is a perspective view of one embodiment of a caudad implantabledevice for replacing the superior half of a natural facet joint on aninferior vertebral body;

FIGS. 10A and 10B are views of one embodiment of a measurement tool forimplanting an artificial caudad facet joint;

FIGS. 11A-D are views of one embodiment of a measurement tool holder forholding a measurement tool for a caudad cephalad facet joint;

FIGS. 12A and 12B are views of one embodiment of an installedmeasurement tool for a caudad cephalad facet joint;

FIGS. 13A-B are views of another embodiment of a measurement tool for acaudad facet joint;

FIGS. 14A-C are views of a measurement tool for a caudad facet joint;

FIGS. 15A-D are views of a measurement tool illustrating the interiorcomponent of a measurement tool for a caudad facet joint;

FIGS. 16 is an exploded view of an alternative embodiment of ameasurement tool according to the invention;

FIGS. 17A-C are views of a tool for implanting the measurement tool ofthe invention;

FIGS. 18A-D illustrate a measurement tool of the invention along withguides used with the measuring tool to assess the size and angle of thedevice to be implanted;

FIGS. 19A illustrates an image taken of a section of spine with themeasurement tool incorporated therein to provide radiopaque markers;FIGS. 19B illustrates a spine having two measurement tools associatedtherewith;

FIGS. 20A illustrates a radiological image of a caudad selection tool incombination with a sizing template;

FIGS. 20B illustrates a portion of the spine with the measurement toolsextending therefrom;

FIGS. 21 illustrates a superior view of a vertebral body with ameasurement tool associated therewith and a radiological image of themeasurement tool within the spine;

FIGS. 22 illustrates a side view of vertebral body with two measurementtools associated therewith and a radiological image of the tool withinthe spine; and

FIG. 23 is a flow chart illustrating method steps for determining thesize of an artificial facet joint using the tools of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to tools for use with implantable devices,including implantable prosthesis suitable for implantation within thebody to restore and/or augment connective tissue such as bone, andsystems and methods for treating spinal pathologies that incorporate useof the tools. The invention relates generally to implantable devices andtools for use with implantable devices and apparatuses or mechanismsthat are suitable for implantation within a human body to restore,augment, and/or replace soft tissue and connective tissue, includingbone and cartilage, and systems for treating spinal pathologies. Invarious embodiments, the implantable devices used with the tools caninclude devices designed to replace missing, removed or resected bodyparts or structure. The implantable devices, tools, apparatus ormechanisms are configured such that the devices or tools can be formedfrom parts, elements or components which alone, or in combination,comprise the device or tools. Thus, for example the tools can beconfigured to work with implantable devices formed from parts, elementsor components. The implantable devices can also be configured such thatone or more elements or components are formed integrally to achieve adesired physiological, operational or functional result such that thecomponents complete the device. Similarly, tools can be configured suchthat one or more elements or components are formed integrally to achievea desired physiological, operational or functional result such that thecomponents complete the tool. Functional results can include thesurgical restoration and functional power of a joint, controlling,limiting or altering the functional power of a joint, and/or eliminatingthe functional power of a joint by preventing joint motion. Portions ofthe device can be configured to replace or augment existing anatomyand/or implanted devices, and/or be used in combination with resectionor removal of existing anatomical structure.

The tools of the invention are designed to interact with the humanspinal column 10, as shown in FIG. 1, which is comprised of a series ofthirty-three stacked vertebrae 12 divided into five regions. Thecervical region includes seven vertebrae, known as C1-C7. The thoracicregion includes twelve vertebrae, known as T1-T12. The lumbar regioncontains five vertebrae, known as L1-L5. The sacral region is comprisedof five fused vertebrae, known as S1-S5, while the coccygeal regioncontains four fused vertebrae, known as Co1-Co4.

An example of one vertebra is illustrated in FIG. 2 which depicts asuperior plan view of a normal human lumbar vertebra 12. Although humanlumbar vertebrae vary somewhat according to location, the vertebraeshare many common features. Each vertebra 12 includes a vertebral body14. Two short boney protrusions, the pedicles 16, 16′, extend dorsallyfrom each side of the vertebral body 14 to form a vertebral arch 18which defines the vertebral foramen.

At the posterior end of each pedicle 16, the vertebral arch 18 flaresout into broad plates of bone known as the laminae 20. The laminae 20fuse with each other to form a spinous process 22. The spinous process22 provides for muscle and ligamentous attachment. A smooth transitionfrom the pedicles 16 to the laminae 20 is interrupted by the formationof a series of processes.

Two transverse processes 24, 24′ thrust out laterally, one on each side,from the junction of the pedicle 16 with the lamina 20. The transverseprocesses 24, 24′ serve as levers for the attachment of muscles to thevertebrae 12. Four articular processes, two superior 26, 26′ and twoinferior 28, 28′, also rise from the junctions of the pedicles 16 andthe laminae 20. The superior articular processes 26, 26′ are sharp ovalplates of bone rising upward on each side of the vertebrae, while theinferior processes 28, 28′ are oval plates of bone that jut downward oneach side. See also FIG. 4.

The superior and inferior articular processes 26 and 28 each have anatural bony structure known as a facet. The superior articular facet 30faces medially upward, while the inferior articular facet 31 (see FIG.3) faces laterally downward. When adjacent vertebrae 12 are aligned, thefacets 30 and 31, capped with a smooth articular cartilage andencapsulated by ligaments, interlock to form a facet joint 32. The facetjoints are apophyseal joints that have a loose capsule and a synoviallining.

As discussed, the facet joint 32 is composed of a superior facet 30 andan inferior facet 31 (shown in FIG. 4). The superior facet is formed bythe vertebral level below the joint 32, and the inferior facet is formedin the vertebral level above the joint 32. For example, in the L4-L5facet joint shown in FIG. 3, the superior facet of the joint 32 isformed by bony structure on the L5 vertebra (i.e., a superior articularsurface and supporting bone 26 on the L5 vertebra), and the inferiorfacet of the joint 32 is formed by bony structure on the L4 vertebra(i.e., an inferior articular surface and supporting bone 28 on the L4vertebra). The angle formed by a facet joint located between a superiorfacet and an inferior facet changes with respect to the midline of thespine depending upon the location of the vertebral body along the spine.The facet joints do not, in and of themselves, substantially supportaxial loads unless the spine is in an extension posture (lordosis). Aswould be appreciated by those of skill in the art, the orientation ofthe facet joint for a particular pair of vertebral bodies changessignificantly from the thoracic to the lumbar spine to accommodate ajoint's ability to resist flexion-extension, lateral bending, androtation.

An intervertebral disc 34 between each adjacent vertebra 12 (withstacked vertebral bodies shown as 14, 15 in FIG. 3) permits glidingmovement between the vertebrae 12. The structure and alignment of thevertebrae 12 thus permit a range of movement of the vertebrae 12relative to each other. FIG. 4 illustrates a posterolateral oblique viewof a vertebrae 12, further illustrating the curved surface of thesuperior articular facet 30 and the protruding structure of the inferiorfacet 31 adapted to mate with the opposing superior articular facet. Asdiscussed above, the position of the inferior facet 31 and superiorfacet 30 varies on a particular vertebral body to achieve the desiredbiomechanical behavior of a region of the spine.

Thus, the overall spine comprises a series of functional spinal unitsthat are a motion segment consisting of two adjacent vertebral bodies,the intervertebral disc, associated ligaments, and facet joints. See,Posner, I, et al. A biomechanical analysis of the clinical stability ofthe lumbar and lumbrosacral spine. Spine 7:374-389 (1982).

As previously described, a natural facet joint, such as facet joint 32(FIG. 3), has a superior facet 30 and an inferior facet 31. Inanatomical terms, the superior facet of the joint is formed by thevertebral level below the joint, which can thus be called the “caudad”portion of the facet joint because it is anatomically closer to the tailbone or feet of the person. The inferior facet of the facet joint isformed by the vertebral level above the joint, which can be called the“cephalad” portion of the facet joint because it is anatomically closerto the head of the person. Thus, a device that, in use, replaces thecaudad portion of a natural facet joint (i.e., the superior facet 30)can be referred to as a “caudad” device. Likewise, a device that, inuse, replaces the cephalad portion of a natural facet joint (i.e., theinferior facet 31) can be referred to a “cephalad” device.

When the processes on one side of a vertebral body 14 are spaceddifferently from processes on the other side of the same vertebral body,components of the devices on each side would desirably be of differingsizes as well to account for anatomical difference that can occurbetween patients. Moreover, it can be difficult for a surgeon todetermine the precise size and/or shape necessary for an implantabledevice until the surgical site has actually been prepared for receivingthe device. In such case, the surgeon typically can quickly deploy afamily of devices possessing differing sizes and/or shapes during thesurgery. Thus, embodiments of the spinal devices of the presentinvention include modular designs that are either or both configurableand adaptable. Additionally, the various embodiments disclosed hereinmay also be formed into a kit or system of modular tools that can beassembled in situ to create a patient specific tool. As will beappreciated by those of skill in the art, as imaging technologyimproves, and mechanisms for interpreting the images (e.g., softwaretools) improve, patient specific designs employing these concepts may beconfigured or manufactured prior to the surgery. Thus, it is within thescope of the invention to provide for patient specific devices withintegrally formed components that are pre-configured. Further, thepractice of the present invention employs, unless otherwise indicated,conventional methods of x-ray imaging and processing, x-raytomosynthesis, ultrasound including A-scan, B-scan and C-scan, computedtomography (CT scan), magnetic resonance imaging (MRI), opticalcoherence tomography, single photon emission tomography (SPECT) andpositron emission tomography (PET) within the skill of the art. Suchtechniques are explained fully in the literature and need not bedescribed herein. See, e.g., Essentials of Radiologic Science, Fosbinderand Kelsey, 2002, The McGraw-Hill Companies, publisher; X-Ray StructureDetermination: A Practical Guide, 2nd Edition, editors Stout and Jensen,1989, John Wiley & Sons, publisher; Body CT: A Practical Approach,editor Slone, 1999, McGraw-Hill publisher; X-ray Diagnosis: APhysician's Approach, editor Lam, 1998 Springer-Verlag, publisher.

A configurable modular device design, such as the one enabled by thisinvention, allows for individual components to be selected from a rangeof different sizes and utilized within a modular device. One example ofsize is to provide caudad and cephalad stems of various lengths. Amodular implantable device design allows for individual components to beselected for different functional characteristics as well. One exampleof function is to provide stems having different surface features and/ortextures to provide anti-rotation capability. Other examples of theconfigurability of modular implantable device of the present inventionas described in greater detail below.

Implantable devices can be configurable such that the resultingimplantable spinal device is selected and positioned to conform to aspecific anatomy or desired surgical outcome. The adaptable aspect ofdevices provide the surgeon with customization options during theimplantation or revision procedure. It is the adaptability of the devicesystems that also provides adjustment of the components during theimplantation procedure to ensure optimal conformity to the desiredanatomical orientation or surgical outcome. An adaptable modular deviceallows for the adjustment of various component-to-componentrelationships. One example of a component-to-component relationship isthe rotational angular relationship between a crossbar mount and acrossbar in an implantable device. Configurability may be thought of asthe selection of a particular size of component that together with othercomponent size selections results in a custom fit implantable device.Adaptability then can refer to the implantation and adjustment of theindividual components within a range of positions in such a way as tofine tune the “custom fit” devices for an individual patient. The netresult is that embodiments of the modular, configurable, adaptablespinal device and systems of the present invention allow the surgeon toalter the size, orientation, and relationship between the variouscomponents of the device to fit the particular needs of a patient duringthe actual surgical procedure. Tools that are configurable and adaptablein a manner similar to the devices are contemplated by the invention toachieve optimal device selection for a patent.

In order to understand the configurability, adaptability, andoperational aspects of the invention, it is helpful to understand theanatomical references of the body 50 with respect to which the positionand operation of the devices, and components thereof, are described.There are three anatomical planes generally used in anatomy to describethe human body and structure within the human body: the axial plane 52,the sagittal plane 54 and the coronal plane 56 (see FIG. 5).Additionally, devices, tools, and the operation of devices and tools arebetter understood with respect to the caudad 60 direction and/or thecephalad direction 62. Devices positioned within the body can bepositioned dorsally 70 (or posteriorly) such that the placement oroperation of the tools or device is toward the back or rear of the body.Alternatively, devices can be positioned ventrally 72 (or anteriorly)such that the placement or operation of the tool or device is toward thefront of the body. Various embodiments of the spinal devices, tools andsystems of the present invention may be configurable and variable withrespect to a single anatomical plane or with respect to two or moreanatomical planes. For example, a component or tool may be described aslying within and/or having adaptability or operability in relation to asingle plane. For example, a stem may be positioned in a desiredlocation relative to an axial plane and may be moveable between a numberof adaptable positions or within a range of positions. Similarly, thevarious components can incorporate differing sizes and/or shapes inorder to accommodate differing patient sizes and/or anticipated loads.

For purposes of illustrating the invention, an example of a cephaladfacet joint that is suitable for use with the measurement tools andmethods described herein is depicted in FIG. 6. See also, US2005/0131406 A1 (Reiley, et al.) FIG. 6 shows an artificial cephaladfacet joint 40 configured to replace the inferior articulating processof a facet joint 31, such as after the surgical removal of thearticulating process. When the cephalad facet joint 40 is attached to avertebra, the artificial facet joint element 44 articulates with thesuperior half of the facet joint 32. In this example, artificial facetjoint 40 includes an artificial facet joint element 44 connected to afixation element 52 via a polyaxial connection 41 that permits facetjoint element 44 and fixation element 52 to be rotated with respect toeach other around more than one axis. A fixing nut 48 is threadablyengaged with the outer periphery of base 42 above the artificial facetjoint element 44. Similarly, a set screw 46 is threadably engaged withthe inner periphery of base 42 above the artificial facet joint element44. The artificial facet joint element 44 includes a support arm 72 anda facet joint bearing surface 74. In alternative embodiments, otherconvex or concave shapes may be used for the facet joint bearing surface74. Bearing surface 74 may be formed from biocompatible metals (such ascobalt chromium steel, surgical steels, titanium, titanium alloys,tantalum alloys, aluminum, etc.), ceramics, polyethylene, biocompatiblepolymers, and other materials known in the orthopedic arts. Fixationelement 52 may be a screw, stem, corkscrew, wire, staple, adhesive,bone, and other materials known in the orthopedic arts.

As shown in FIGS. 7A and 7B, a measurement tool 400 suitable for use ininstalling and configuring the artificial facet joint 40 of FIG. 6includes a support arm element 401 and a fixation measurement element402 via a polyaxial connection element 403. The polyaxial connectionelement 403 permits movement of the support arm element 401 along thefixation measurement element 402 in multiple axes. The connection 403permits vertical movement of the support arm element 401 along thefixation measurement element 402 (or fixation element) and also permitshorizontal movement of the support arm element 401 relative to thefixation measurement element 402. In this manner, the measurement toolcontains aspects of the actual artificial facet joint 40. Measurementtools optimized to aid in the implantation of other implantable spinaldevices may have other features containing aspects of those devices.

The fixation measurement element 402 is adapted and configured to permitmeasurement of the length of a fixation element of an artificialcephalad facet joint to be installed in a patient. Preferably, markings407 are present on the fixation measurement element 402 which permit thedetermination of this length measurement. Typically, a hole or cavity isformed in the vertebra of the patient at a location wherein theartificial cephalad facet joint 40 is intended to be installed and themeasurement tool 400 is placed in this hole. The tool 400 is adjusted toa position similar to that of the artificial cephalad facet joint, andthen the penetration depth of the fixation measurement element 402 intothe hole is determined. This penetration depth assists the user inchoosing the length of the fixation element required to attach theartificial cephalad facet joint to the vertebra.

In one embodiment, the fixation measurement element 402 includesindentations 411 such as those depicted in FIG. 7A. The indentations 409provide stops for the vertical movement of the support arm 401 along thefixation measurement element 402, e.g., by engaging a ridge 411 in asupport arm 401. The indentations 409 can also permit the determinationof the length of the fixation element 52 of an artificial cephalad facetjoint 40 to be installed in a patient. The indentations 409 may beformed at intervals corresponding to various fixation stems or screwlengths contained in a modular component kit.

Similarly, another length measurement can be obtained using the supportarm element 401. Once the measurement tool 400 is placed into the holeor cavity drilled in the vertebra, the support arm 401 is positionedinto a location wherein the artificial facet joint element 44 of theartificial cephalad facet joint 40 would be located. The distancebetween the fixation measurement element 402 and the putative locationof facet joint bearing surface 74 of the artificial cephalad facet joint40 is measured along the support arm element 401. This measurement isused to select the length of the support arm 72 of the cephalad facetjoint 40 to be implanted in a patient. Alternatively, the measurementcould correspond to a color coding or number/letter designation that isused to determine the appropriate correspondingly-identified artificialfacet joint.

In one embodiment, a trial facet joint bearing surface 404 can beattached to the support arm element 401. The trial facet joint bearingsurface 404 may be placed in the location that the actual artificialcephalad facet joint 40 would be placed and then the length measurementcan be obtained which can be used to select the length of the supportarm 72 of the artificial cephalad facet joint 40. Once again, therelationship between the measurement tool's fixation measurementelement, support arm element and trial facet joint bearing surfacecorresponds to aspects of the actual facet joint whose implant the toolis assisting. Other measurement tools and methods having aspectscorresponding to other spine implant features are within the scope ofthis invention.

Another aspect of the invention is a method of using the measurementtool 400 to measure the dimensions of an artificial cephalad facet joint40 to be used in total facet joint replacement. The artificial cephaladfacet joint 40 is typically attached to a vertebra to replace thearticulating function of the cephalad portion of the natural facet joint32. FIG. 8 shows different views of a measurement tool 400 placed into avertebra 12. In one embodiment, for obtaining the measurements, thecephalad measurement tool 400 can be placed in one vertebra and a caudadfacet joint 600 can be placed in the inferior adjoining vertebra, asdepicted in FIG. 8A. The artificial caudad facet joint can be a trialdevice or the actual artificial facet joint. When the measurement tool400 is used with an artificial caudad facet joint, it is preferred thatthe support arm element 401 have a trial facet joint bearing surface404. To obtain the length measurements, a hole is formed in the locationon the spine where the actual artificial cephalad facet joint 40 (notshown) is to be placed. The tool 400 is placed in the hole formed in thespine at a depth that is similar to the depth at which actual artificialcephalad facet joint 40 is to be placed. The support arm 401 is movedhorizontally and/or vertically with respect to the fixation measurementelement 402 and placed at about the same location that the artificialfacet joint element 44 would be placed. If the measurement tool 400includes a trial cephalad facet joint bearing surface 404 and is used incombination with an artificial caudad facet joint 600, the trial facetjoint bearing surface 404 is placed in the bearing surface of the caudadfacet joint prior to taking the measurements. In one embodiment, asshown in FIGS. 7B and 8B, to determine the length of the support arm 72of the actual artificial cephalad facet, a window on the trial facetjoint bearing surface 404 can be used to read the length from thesupport arm element 401. As mentioned above, the length of the fixationelement 52 can be determined from the fixation measurement element 402.Markings 407 and/or indentations 409 on the fixation measurement element402 can be used to determine the required length of the fixation element52. Markings 407 are positioned to correspond with indentations on thefixation measurement element 402 such that when the polyaxial connectionelement 403 is engaged with the measurement element 402, e.g., byengaging the indentation 405 in the fixation measurement element 402with a ridge 402 a protrusion on the polyaxial connection element 403, ameasurement is ascertainable by the user.

FIG. 9 shows an artificial caudad facet joint 100 configured to replacethe superior portion of a natural facet joint 30, such as after thesurgical removal of the articulating process forming the superiorportion of the facet joint. Artificial caudad facet 100 includes anartificial facet joint element 104 connected to a fixation element 116via a polyaxial connection 115 that permits facet joint element 104 andfixation element 116 to be rotated with respect to each other aroundmore than one axis. The polyaxial connection 115 of artificial caudadfacet joint 100 includes a base 112 connected to a support arm 102 offacet joint element 104. The artificial facet joint element 104 includesa bearing surface 118. A fixing nut 108 is threadably engaged with theouter periphery of base 112 above the artificial facet joint element104. Similarly, a set screw 106 is threadably engaged with the innerperiphery of base 112 above the artificial facet joint element 104.

FIGS. 10-12 depict one embodiment of a measurement tool for installingan artificial caudad facet joint 100. The measurement tool can be usedto assist in the installation of artificial caudad facet joint such asthose described in U.S. Patent Pub. US 2005/0131406 A1 (Reiley, et al.)or other caudad facet joint.

A measurement tool 700 suitable for use with the artificial caudad facetjoint shown in FIG. 9 is shown in FIGS. 10A and 10B. Measurement tool700 includes a stem element 701 connected to a trial caudad bearingsurface 702 via a fastener 703. Thus, measurement tool 700 containsaspects of the artificial caudad facet joint 100 whose implant the toolis assisting. In the embodiment depicted in FIG. 10A, the fastener 703is a set screw. In other embodiments other suitable fasteners can beemployed, including, but not limited to, stems, posts, threads,polyaxial mechanisms, splines, cap screws, ball detents, friction fits,tapers, press fits, bayonet, cams, collets and/or clamps.

The stem element 701 is adapted and configured to obtain lengthmeasurements which would correspond to the length of the fixationelement 116 of the artificial caudad facet joint 100. The stem element701 can include markings and/or indentations such as those depicted withrespect to the cephalad tool 400 shown in FIG. 8 to assist in obtainingthe measurements. If desired, multiple stem elements of varyingdiameters and lengths can be utilized in a similar fashion to sizeand/or determine the diameter and dimensions of the hole or cavity.

The trial caudad bearing surface 702 helps determine the relativepositions of, and the angle between, the artificial facet joint'sfixation element and its bearing surface. The trial caudad bearingsurface 702 is capable of movement along multiple planes and can rotaterelative to the stem element 701 via a lockable ball-joint or othersuitable joint configuration. If desired, an alternate embodiment of thebearing surface 702 can move vertically (not shown) along the stemelement 701, to permit sizing of the stem element 701. Other planes ofmovement can include the median, horizontal and frontal planes as wellas the sagittal, coronal, and axial shown in FIG. 5. In anotherembodiment, the caudad bearing surface 702 is connected to a handle 704.The handle 704 allows the user to move the caudad bearing surface 702into the desired location and also position it in the right plane.Typically, the handle 704 permits movement of the caudad bearing surface702 in various planes for alignment. Also, the handle 704 can permit theuser to place the stem 701 of the tool 700 into the hole drilled in thevertebra.

In one alternate embodiment, the handle 704 can comprise a radiopaquematerial with the handle 704 used for fluoroscopic alignment of thecaudad bearing surface 702. By using radiopaque materials that do notallow the passage of x-rays or other radiation through the part, aphysician can see the instrument when radiologic imaging techniques areused. In this embodiment, the handle 704 and upper end plate of thecaudad vertebral body (not shown) can be examined in a medial-lateralimage (using non-invasive and/or fluoroscopic imagine apparatus) of thesurgical area. A comparison of the orientation of the handle 704 and theorientation of the upper end plate can be made to determine the desiredalignment and positioning of the caudad bearing surface. In oneembodiment, the orientation of the handle and the upper end plate can beparallel or nearly parallel.

Another aspect of the invention is a measurement tool holder for usewith the caudad measurement tool 700 described above or anothermeasurement tool. One embodiment of the measurement tool holder isdepicted in FIGS. 11A-D. In this embodiment, the measurement tool holder800 includes a measurement surface 801 and a holder element 802. In oneembodiment, the measurement surface 801 includes two plates attached toeach other at a right angle, as illustrated in FIG. 11C-D. Themeasurement surface 801 is adapted and configured to measure the anglebetween the caudad bearing surface 702 and stem 701. This anglemeasurement is typically used by a user to select, assemble and/orconfigure an artificial caudad facet joint 100 for implantation into apatient, such as artificial caudad facet joint 100 of FIG. 9. Forexample, the selected artificial caudad facet joint 100 may have anangle measurement between its bearing surface 118 and its fixationelement 116 similar to the angle measurement obtained from the caudadmeasurement tool 700 and measurement tool holder 800. Alternatively, theartificial caudad facet joint may be configurable to orient its fixationelement 116 and its bearing surface 118 to match the measured angle.

In one embodiment, the tool holder's 800 measurement surface 801includes markings 803 to assist in obtaining the desired anglemeasurements. Also, the top surface of the measurement surface 801 mayhave a holder element 802 attached thereto. The holder element 802 canbe, for example, a square or rectangular block with a portion of theblock cut-out to fit the caudad bearing surface 702 of the caudadmeasurement tool 700. Alternatively, the block can be configured toengage the measurement tool 700 the portion of the holder element 802that holds the caudad bearing surface 702 is cut-out in a shape that issuitable for holding the caudad bearing surface 702. Thus, the shape ofthe cut-out portion of the holder element 802 will vary depending on theshape of the caudad bearing surface 702 to be used with the measurementholder 800.

One aspect of the invention is a method for using the caudad measurementtool 700 in combination with, for example, the measurement tool holder800 described above or with the cephalad measurement tool 400 describedabove. In one embodiment, a hole is formed at a suitable location in thevertebra (such as by drilling) wherein an artificial caudad facet joint100 is intended to be placed. This location typically is the bestlocation for the placement of the artificial caudad facet joint based onthe condition of the bone, easy access to the location, etc. Into thishole the caudad measurement tool 700 is placed in a manner as shown inFIGS. 12A and 12B.

The caudad measurement tool 700 may be placed into the hole using thehandle 704. The handle 704 and the set screw 703 are used to place themeasurement tool at the required depth and also to place the caudadbearing surface 702 at the required angle. To obtain the appropriateangle of the caudad bearing surface 702 with respect to the stem 701,the fastener 703 is loosened and the caudad bearing surface 702 ispositioned at the appropriate angle. Once the appropriate angle isobtained (typically based on orientation relationships with anatomicallandmarks, which can include the orientation of the cephalad bearingsurface as well as anatomical positioning and/or intervening anatomicalfeatures), the fastener 703 is tightened to maintain the angle formeasurement purposes. In one embodiment, the caudad measurement tool 700is used in combination with an artificial cephalad facet joint (such asartificial cephalad facet joint 40 described above) or a cephaladmeasurement tool (such as tool 400 described above). When used incombination with an artificial cephalad facet joint or a cephaladmeasurement tool, the caudad bearing surface 702 is placed in contactwith the facet joint bearing surface of the artificial cephalad facetjoint or the trial facet joint bearing surface. Then, the position ofthe caudad bearing surface 702 is adjusted by manipulating the fastener703 (as described above) to get good articulation with the facet jointbearing surface or the trial facet joint bearing surface.

After the caudad measurement tool 700 is appropriately placed, thelength and angle measurements are obtained. Preferably, the caudadmeasurement tool 700 is removed from the hole to take the measurements.One of the measurements that can be obtained with the caudad measurementtool 700 is the fixation length measurement. This measurement isobtained from the stem element 701 and indicates the length of thefixation element 116 of the artificial caudad facet joint to beimplanted in a patient. Also, the caudad measurement tool 700 can beused to obtain an angle measurement between the caudad bearing surface702 (or alignment fixation measurement) and stem element 701. Thismeasurement may be obtained by placing the caudad measurement tool 700into a measurement tool holder (such as holder 800 described above) andreading the angle, such as from a measuring surface 801. When used withthe artificial caudad facet joint 100 of FIG. 9, this angle measurementis used to determine the angle between the artificial facet jointelement 104 and fixation element 116 of the artificial caudad 100. Inone alternate embodiment, the caudad bearing surface is positioned andsecured to the vertebral body first, and then the cephalad bearingsurface is positioned and secured relative to the caudad bearingsurface.

One aspect of the invention is a method for selecting suitable caudadand/or cephalad artificial joints from a set of artificial joints forimplantation into a patient. In one embodiment, the cephalad measurementtool 400 is used to obtain the two length measurements from the fixationmeasurement 402 and support arm 401. A user uses these measurements toselect a suitable artificial cephalad facet joint 40 for implantation ina patient. The selected artificial facet joint preferably has a fixationelement 52 length and support arm 72 length that are similar to thesupport arm 401 and fixation measurement 402 length measurements,respectively, obtained from the cephalad measurement tool 400. As willbe appreciated, similar includes lengths that have values thatcorrespond to each other but are not necessarily identical. In anotherembodiment, the caudad measurement tool 700 is used to obtain length andangle measurements and a user uses these measurements to select asuitable artificial cephalad facet joint for implantation in a patient.The selected artificial facet joint preferably has a stem 701 lengthsimilar to the length measurement from the caudad tool 700 and has anangle between the artificial facet joint element and fixation elementsimilar to the angle measurement obtained from the tool.

Yet another alternate device and method for determining the proper sizeand orientation of the artificial facet joint is illustrated in FIGS.13A-B. A tool such as a component selection instrument 1300 isillustrated that is useful for determining the proper combination ofcaudad anchor stem, as well as the caudad cup best suited for a targetedanatomy. In this embodiment, a component selection instrument 1300comprises a handle 1310, a body 1320 and a stem 1330, each of thesepreferably comprising a radiolucent material. Within the body 1320 andthe distal tip 1340 of the stem, radiopaque markers 1350, 1360 and 1370are positioned, such that, when the stem 1340 is inserted into a pilothole (not shown) of a targeted vertebral body in a spine, uponradiographic visualization of the vertebral body, the radiopaque markersalign to indicate the proper combination of components for the targetedregion, while the radiolucent instrument allows the physician to viewthe markers relative to the patient's anatomy.

Specifically, the depicted embodiment of a component selectioninstrument 1300 incorporates a distal radiopaque marker 1350 positionedwithin the distal tip 1340 of the stem 1330. A series of stem selectionradiopaque markers 1360 (in this embodiment, three markers) arepositioned within the housing. As will be appreciated by those skilledin the art, more or fewer markers can be used. A series of cup selectionradiopaque markers 1370 (in this embodiment, three markers) are alsopositioned within the housing. If desired, the component selectioninstrument 1300 can be optimized for single-sided use (for measurementof only the left or right pedicle) or for dual-sided use (for example,the component selection instrument could be adapted and configured toincorporate symmetrical radiopaque markers that provide the propermeasurements depending upon the orientation of the instrument.Additionally, as discussed more fully below, the markers can be givenexterior dimensions that present different profiles during radiographyin order to facilitate an ease in determining which set of markers isbeing viewed.

Once the stem 1330 is inserted into the pilot hole or cavity (notshown), the interior edge 1380 of the housing 1320 (the edge nearest thecenterline or midline of the spine in the body (see FIG. 5)) is visuallyaligned with the spinous process 22 of the vertebral body (see FIGS.1-4). Once the visual alignment is achieved, radiologic techniques knownin the art can be used to obtain a view of the target anatomy along withthe component selection instrument, such as an anterior/posterior (A/P)view of the spine and component selection instrument 1300 using afluoroscope. Depending upon the lateral angle of the pedicle, the distalradiopaque marker 1350 will line-up with (or will appear closest to) oneof the stem selection radiopaque markers 1360, each of which correspondto a different stem angle. After taking the A/P view, the physician canthen take a lateral view of the spine and component selection instrument1300. From the lateral view, the physician can then align the cephaladendplate of the caudad vertebral body (not shown) with the mostappropriate cup selection radiopaque marker, which gives the proper cupsize for implantation. (See, FIG. 23). Alternatively, a lateral view canbe taken first, or only one of the A/P or lateral view can be taken andanalyzed.

The caudad stem may be secured directly into the vertebral body, or canbe attached and/or “fixed” using a supplemental fixation material suchas bone cement, allograft tissue, autograft tissue, adhesives,osteo-conductive materials, osteo-inductive materials and/or bonescaffolding materials. In one embodiment, the first fixation element canbe enhanced with a bony in-growth surface, such as surfaces createdusing sintering processes or chemical etching (Tecomet Corporation ofWoburn, Mass.) which can help fix the fixation element within avertebra. As described above, the bony in-growth surface can cover allor a portion of the caudad fixation element. Desirably, the finalorientation of the caudad cups of-the caudad facet joint 600 (FIGS. 8Band 9) will be parallel (relative to the lateral walls 159 of the caudadcup) and coplanar (with respect to the upper bottom surfaces 153).

FIG. 14A depicts a top plan view of an alternate embodiment of acomponent selection instrument 900 constructed in accordance withvarious teachings of the present invention. The component selectioninstrument 900 comprises a stem 905 and a head 910, both of which, inthis embodiment, are desirably (but not necessarily) constructed ofradio-lucent materials (or alternative materials useful in conjunctionwith the present invention, including those that desirably facilitatethe use of non-direct visualization such as fluoroscopy, real-time CTscanning and/or real-time MRI). The stem comprises a distal section 950(distal from the block) having a distal end 951, a central section 955,and a proximal section 960. The stem 905 is configured to engage thehead 910 at its proximal end 961. The stem 950 can be positioned suchthat it extends from the head 910 at an angle other than 90° in at leastone direction. Thus, as evident from FIG. 14 a, a side view of thecomponent selection instrument 900, the head 910 is positioned on afirst geometric plane, while the stem 905 extends from the head 910 suchthat the stem 905 crosses, or could cross if the stem had sufficientlength, the geometric plane on which the head 910 is positioned. Incontrast, as illustrated in FIG. 14C, a view of the instrument 900 takenfrom a top view, the stem 905 extends from the head 910 such that itappears from this two-dimensional perspective that the stem 905 and thehead 910 lie within the same plane. FIG. 14B illustrates a perspectiveview of the instrument 900. The head 910 can be configured with anindentation, slot or keyway 990 which is adapted to engage a tool, suchas the tool shown in FIG. 17.

As illustrated in FIG. 15A, which depicts the same component selectioninstrument 900 enabling the internal portion of the instrument to beviewed, one or more radiopaque markers are contained within the stem 905and head 910. These markers are desirably positioned such that, when thecomponent selection instrument 900 is secured to the targeted vertebralbody, one or more non-direct visualization methods can be used tocompare the visible anatomical landmarks to the various markersincorporated in the component selection instrument (as well as thevarious inter-relationships between markers and/or the anatomicalfeatures themselves) to determine the anatomical characteristics of thecomponents of the targeted vertebral body, as well as the relationshiptherebetween. This invention allows the physician employ minimallyinvasive techniques to select the optimal implantable artificial jointcomponents to accommodate the targeted patient anatomy. In addition, theunique orientation and positioning of the radiopaque markers within thestem 905 and head 910 can obviate the need for an “adjustable,” orarticulating, facet measurement devices, thereby significantlysimplifying the construction and/or use of the device.

Thus, turning to FIG. 15, the component selection instrument 900incorporates a radiopaque marker 915 positioned within the stem 905. Theradiopaque marker 915 can be in a variety of suitable configurations,such as a ball, as depicted which would present a circular image in atwo dimensional image, such as an x-ray. The radiopaque ball 915 andvarious marker elements in the head 910 are arranged to allowdetermination of the orientation of the stem 905 relative to a givenanatomical feature and/or arbitrary reference plane. In addition, afirst marker 920 can be positioned within the head 910. As will bedescribed later, this first marker 920 can be used to determine theangle of the stem 905 relative to a cephalad endplate (not shown) of thevertebral body in which the component selection instrument is placed.One or more second markers 935, 940 and 945 (which may be parallel toeach other and/or within the same plane) can also be positioned withinthe head 910, and are desirably used, in conjunction with the ball 905.As will be appreciated by those skilled in the art, either or both setsof first and second markers can be used without departing from the scopeof the invention. Further, the first set of markers can be in a firstorientation, e.g. horizontal, while the second set of markers can be ina second orientation that is different than that of the first set ofmarkers, e.g. vertical, where horizontal and vertical can be in relationto a defined plane in the body or an arbitrary plane used to describethe location of one set of markers with respect to the second set ofmarkers, given that the actual location of the component selectioninstrument within a human body can change depending upon the location inthe spine where the instrument is used. Either or both sets of markersis useful for determining the orientation of the stem 905 in relation toa sagittal plane passing vertically through a targeted vertebral body(see, FIG. 5). As depicted the stem 905 is configured to engage the head910 by, for example, threadably engaging the proximal end of the stem905. For this purpose, the proximal end of the stem 905 has a pluralityof threads 906 that engage grooves 908 located within the head 910.

In an embodiment, the stem 910 can be configured such that it has ahollow aperture 912 through a portion thereof. The hollow aperture canbe used to house the distal end 950 of the stem 910. Thus, providing atelescoping effect for the stem 910 which enables the stem to achievevariable lengths in operation. Where a telescoping stem 910 is used, afirst pilot hole can be drilled into the vertebral body of a firstdiameter. The telescoping stem 910 can then be inserted into the pilothole a distance corresponding to the length of the distal end 950 of thestem 910 which has a diameter that is sized to engage the first pilothole. Subsequently, a second pilot hole can be drilled which enlarges orrevises the diameter of the first pilot hole and uses the first pilothole as a basis. Upon obtaining a second pilot hole, the stem 910 can bereinserted into the pilot hole. In one instance, the telescoping distalend 950 can be retracted into the lumen of the proximal end of the stemenabling the larger diametered distal end to be inserted into the pilothole. Alternatively, the pilot hole can be of sufficient depth to enableit to accommodate the entire length of the stem 910, which the upperregion of the pilot hole having a diameter sized to engage the largerdiameter of the proximal end of the stem 910. Where the stem 910 istelescoping, the stem could be configured such that when extended, thedistal end of the stem is maintained in an extended configuration by,for example, twisting the distal end relative to the proximal end toengage a latch (similar to a child-proof cap configuration).Alternatively, the distal end of the stem could engage one or moredetents which engage the distal end in an extended or retractedposition. Other solutions would be apparent to those of skill in the artwithout departing from the scope of the invention.

Alternatively, the interior of the stem 910 can be configured from amaterial that has a radiopacity that is different than the rest of thedevice (either more radiopaque, or less), thus providing additionalvisual markers for the physician upon taking an image, such as an x-ray(see, FIG. 15B). The hardness of a first material (e.g. the interiormaterial) can have a hardness, for example a Shore or Rockwell scalevalue, that is higher or lower than the second (exterior material).

In an exemplary embodiment, a component selection instrument 900 cancomprise an approximately 0.8″ by 0.5″ block of radio-lucent polymer,having an approximately 4.5 cm long stem extending outward from theblock. The stem 905 can be configured such that it is stepped by havingsections along its lengths of different diameters (see, e.g. FIG. 15).Alternatively, rather than providing changes to the diameter in a stepfashion, if desired, the stem 905 can gradually change from a firstdiameter at a first end to a second diameter at a second end by, forexample, use of a slope or slant along the length of the stem.

The polymer or thermoplastic used to make any of the components of theinstrument 900, such as the stem 905 or head 910, can comprise virtuallyany non-radiopaque polymer well known to those skilled in the artincluding, but not limited to, polyether-etherketone (PEEK),polyphenylsolfone (Radel®), or polyetherimide resin (Ultem®). Ifdesired, the polymer may also comprise a translucent or transparentmaterial, or a combination of materials where a first material has afirst radiopacity and the second material has a second radiopacity.Suitable PEEK can include an unfilled PEEK approved for medicalimplantation such as that available from Victrex of Lancashire, GreatBritain. (information on Victrex is located at www.matweb.com or seeBoedeker www.boedeker.com). The instruments and tools can be formed byextrusion, injection, compression molding and/or machining techniques,as would be appreciated by those skilled in the art. Other polymers thatmay be suitable for use in some embodiments, for example other grades ofPEEK, such as 30% glass-filled or 30% carbon filled, provided suchmaterials are cleared for use in implantable devices by the FDA, orother regulatory body. The use of glass filled PEEK would be desirablewhere there was a need to reduce the expansion rate and increase theflexural modulus of PEEK for the instrument. Glass-filled PEEK is knownto be ideal for improved strength, stiffness, or stability while carbonfilled PEEK is known to enhance the compressive strength and stiffnessof PEEK and lower its expansion rate. Still other suitable biocompatiblethermoplastic or thermoplastic polycondensate materials mabe besuitable, including materials that have good memory, are flexible,and/or deflectable have very low moisture absorption, and good weaeand/or abrasion resistance, can be used without departing from the scopeof the invention. These include polyetherketoneketone (PEKK),polyetherketone (PEK), polyetherketoneetherketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK), and generally apolyaryletheretherketone. Further other polyketones can be used as wellas other thermoplastics. Reference to appropriate polymers that can beused in the tools or tool components can be made to the followingdocuments, all of which are incorporated herein by reference. Thesedocuments include: PCT Publication WO 02/02158 A1, dated Jan. 10, 2002and entitled Bio-Compatible Polymeric Materials; PCT Publication WO02/00275 A1, dated Jan. 3, 2002 and entitled Bio-Compatible PolymericMaterials; and PCT Publication WO 02/00270 A1, dated Jan. 3, 2002 andentitled Bio-Compatible Polymeric Materials. Still other materials suchas Bionate®, polycarbonate urethane, available from the PolymerTechnology Group, Berkeley, Calif., may also be appropriate because ofthe good oxidative stability, biocompatibility, mechanical strength andabrasion resistance. Other thermoplastic materials and other highmolecular weight polymers can be used as well for portions of theinstrument that are desired to be radiolucent.

In the embodiment illustrated, the stem 905 comprises a 2.25 cm longdistal section having a 4.5 mm diameter, which transitions to a 0.75 cmlong central section having a 5.75 mm diameter, and then transitions toa 2.0 cm long proximal section having a 6.5 mm diameter. Otherconfigurations are possible, including configurations having otherlengths, diameters, as well as fewer or more stepped sections.

The radiopaque ball 915 (which could comprise, for example, a 2 mmdiameter stainless steel ball) is desirably secured inside the centralsection 955 of the stem. The various first and second set of radiopaquemarkers 920, 935, 940 and 945 can comprise, for example, 1.5 mm diametersections of 1 cm long stainless steel wire having a smooth outersurface.

As shown in FIG. 15B the component selection instrument can beconfigured to present a first set of radiopaque markers 920 at a firstorientation and a second set of radiopaque markers 935, 940, 945 at asecond orientation. As illustrated, the first set of radiopaque markers920 lie in a first plane and are positioned parallel one another; whilethe second set of radiopaque markers 935, 940, 945 lie in a second planethat is orientated perpendicular to the first plane. Thus, the positionof the first set of radiopaque markers 920 relative to the second set ofradiopaque markers 935, 940, 945 is such that in a two-dimensionalimage, the markers could appear to be perpendicular to each other, asshown in FIG. 5C. This enables the physician to assess the location ofthe component selection instrument relative to anatomy afterradiological imaging. FIG. 15C is a top view of the component selectioninstrument 900 where the first set of radiopaque markers 920 appear ascircles due to the orientation, while the second set of radiopaquemarkers 935, 940, 945 appear as rods or lengths of wire. In yet anotherembodiment, illustrated in FIG. 15D the first set of radiopaque markers920 are configured such that the markers are not parallel one another,while the second set of radiopaque markers are parallel such that inthis orientation and from the perspective shown it appears as thoughthere is only one marker although, in fact, more than one marker may bepresent, but may not be readily apparent because the markers are stackedin two dimensions.

The various stem diameters desirably facilitate and accommodatemeasurement and verification of proper component sizes during thevarious stages of facet replacement surgery. For example, in preparationfor implantation of a facet replacement device, the surgeon may drill afirst pilot hole, e.g. a 4.5 mm passage, into and/or through thepedicle. This small diameter passage, which may be too small to properlyaccommodate the anchoring device of an artificial facet joint (dependingon the diameter and type of anchoring device), is well suited forimplantation of a standard commercially-available pedicle screw fusionsystem (such as the UCR Pedicle Screw System from SeaSpine (informationavailable at http://www.seaspine.com/ UCR_Pedicle_Screw_System.html)).Thus, the 4.5 mm distal portion of the stem 910 of the componentselection instrument 900 will fit into the 4.5 mm passage drilled intothe pedicle, and if the measurement obtained using the componentselection instrument indicates that the passage through the vertebralanatomy cannot be accommodated by the components of the artificial facetjoint, the surgeon can then choose to (1) redrill or revise the passageand remeasure the passage (e.g., by boring out the original pilot holewith a larger diameter passage and then inserting the componentselection instrument into the revised pilot hole), (2) implant thecomponents of the artificial facet joint most closely approximating theanatomy, and/or (3) choose to fuse the targeted spinal level and implanta pedicle screw and rod system. Accordingly, the present measurementsystem allows the physician to discontinue the facet joint replacementprocedure where the anatomy and/or available artificial facet jointcomponents cannot accommodate the targeted spinal level. Alternatively,if the measurement achieved by the component selection instrumentindicates that the artificial facet joint can accommodate the patient'sspecific anatomy, the component selection instrument can be removed, thepassage can then be redrilled (if desired) to a larger diameter (in thisembodiment, either 5.75 mm or 6.5 mm), and remeasured (if desired) usingthe larger diameter section of the stem to secure the componentselection instrument within the newly drilled passage to ensure properchoice in artificial facet joint components. The artificial facet jointcan then be implanted.

FIG. 16 illustrates yet another embodiment wherein the componentselection instrument is exploded and markers (e.g., first set ofradiopaque markers 920 or second set of radiopaque markers 935, 940,945) are configured such that the exterior of the radiopaque marker doesnot present a smooth surface (e.g. markers illustrated previously appearas either a smooth wire or bar (defined by two parallel lines whensitting longitudinally in a first plane as captured by an image) or acircle (representing the diameter of the marker as it appears in a plane90° offset from the first plane). In this embodiment, employing markersfor at least some of the markers that are not configured from, forexample, wire having a smooth external surface, the physician would beable to determine which orientation was being looked at in aradiographic image. In this embodiment, a single first marker 920 isemployed with three second markers 935, 940, 945 oriented in a planeperpendicular, or substantially perpendicular to the first marker 920.While the alternate configuration of marker could be used, it would alsobe advantageous to mix the marker profiles within a single componentselection instrument such that the markers in a first orientation were,for example, smooth wire, while the markers in a second orientation areturned, e.g. using a lathe with a cutting tool to shape the wire alongits length, to create sections with different cross-sectional orcircumferential values, etched, or notched. Thus, in an image, theorientation of the component selection instrument relative to theanatomy would be easily determinable based on the appearance of smoothlines or turned, notched or etched surfaces along the length of amarker. In this embodiment, the distal end of the stem is solid whilethe proximal end of the stem has an aperture 962 that is sized toreceive the marker 915 and a tube 964 which fits within the aperture 962and is sized to retain the marker within the stem 910.

In another embodiment, where two component selection tools 900 arepositioned within a vertebral body, or a pair of vertebral bodies, and asingle image is taken, the markers 920, 935, 940, 945 can be configuredsuch that the markers in the first component selection tool have a firstgeometric profile, such as smooth lines, or turned, notched or etchedsurfaces along the length. While the markers 920, 935, 940, 945 of thesecond component selection tool have a geometric profile that is not thesame as the geometric profile of the markers 920, 935, 940, 945 of thefirst component selection tool. Thus, for example, markers 920, 935,940, 945 of the first component selection tool could be smooth wirewhile markers 920, 935, 940, 945 of the second component selection toolcould be turned wire. When using two component selection tools at onetime to measure the angle of the desired device, a user could assess bylooking at a single image the desired size and configuration of a devicefor first and second target joint locations by knowing that type ofmarkers in the first component selection tool and its location withinthe body and the type of markers in the second component selection tooland its location within the body. The component selection instrumentscould be positioned in a right and left half of a single vertebral body,or could be positioned within adjacent vertebral bodies.

In the embodiment shown in FIG. 17 the component selection tool 900 ofFIG. 15 is combined with a delivery tool 1000 such as a pair of forcepswith a configured distal end for engaging the component selection tool900. As will be appreciated by those skilled in the art, any instrumentresembling a pair of pincers or tongs, used for grasping, manipulating,or extracting, that is adapted at an end to engage the componentselection instrument would be suitable. Adapted forceps are depicted forpurposes of illustration. FIG. 17 a illustrates a perspective view ofthe forceps 1000 engaging the component selection instrument 900. FIG.17 b illustrates the forceps 1000 engaging the component selectioninstrument 900 from a first planar view, while FIG. 17 c illustrates theforceps 1000 engaging the component selection instrument 900 from asecond planar view. Although these embodiments illustrated the componentselection instrument 900 and the forceps engaging the instrument as twoseparate components, as will be appreciated by those skilled in the artan integrally formed configuration could be used without departing fromthe scope of the invention.

FIG. 18A illustrates a perspective view of a component selection tool1100. The component selection tool 1100 has a head 910 and a stem 905configured differently than the component selection tool 900 of FIG. 14.A variety of radiopaque markers 1102, 1104, 1106, 1108 are provided asshown in FIG. 18B. FIG. 18 c illustrates a gauge 1800 for use indetermining cephalad arm length from an A/P view. The gauge 1800 iscalibrated to provide an indication of a known distance 1802 of themarkers in the component selection instrument. From that point, a smallregion 1804, medium region 1806, and large region 1808 is also marked.The calibration gauge 1800 can also be used in a similar manner withother joints. Turning now to FIG. 18D another gauge 1810 is provided. Afirst line 1812 is oriented along a component selection instrumentcephalad stem orientation line. From that point, the angle of the stemcan be determined, e.g. 75°, 85°.

For example, FIG. 19A depicts an A/P radiographic image 2000 of oneembodiment of a component selection instrument 2010 positioned within apedicle of a targeted vertebral body. In this embodiment, the ball 2015is positioned between two radiopaque markers 2030, 2035 nearest marker2035. FIG. 19B is an image of a spinal column with two componentselection instruments 2010, 2010′ placed therein.

FIG. 20A is a lateral radiographic image 2100 of a spine with acomponent selection instrument 2110 associated therewith. A caudalselector lateral template is used in conjunction with the image toassess the optimal orientation of the caudad selector. Values from −9 to+11 are indicated 2112. This assists in denoting the desired implantcomponent (corresponding to that anatomical orientation of the vertebralbody) which accommodates an axial angle (relative to the sagittalplane). In a desired embodiment, a single A/P view can be utilized tocharacterize the pedicle of a single targeted vertebral body. In a moredesirable embodiment, a single A/P view can be utilized to characterizeboth pedicles of a single targeted vertebral body, each pedicle of whichwill incorporate a single component selector instrument. In a mostdesirable embodiment, a single A/P view can be utilized to characterizethe pedicles of multiple targeted vertebral bodies (adjacent ornon-adjacent), with the pedicles of the vertebral bodies eachincorporating a single component selector instrument. As will beappreciated by those skilled in the art, additional views from the sameor different perspectives can also be used without departing from thescope of the invention, including slices taken using an MRI. FIG. 20Billustrates an image of a portion of a spine model having a componentselection instrument 2110 associated therewith.

Turning to FIG. 21 an image of a vertebral body from a superior position2200 is illustrated having a midline 2202. Three possible orientations2206 of a stem 2204 are illustrated at, e.g., 10°, 20° and 30°. Aradiological image 2210 from a posterior view illustrates the lines andcircles of the markers corresponding to, in this instance a location ofthe circular marker between the innermost two marker lines whichindicates a 30° angle to the midline 2202. In this image, two componentselection instruments are positioned within the vertebral body forselecting the caudad facet joint. The axial plane angles are measuredfor selecting a caudad facet joint. In selecting the optimal angle, thephysician locates the ball shaped marker 2215, 2215′ of the componentselection instrument. Due to the orientation of the marker 2215, 2215′to a second set of markers 2230, 2235, 2240, which appear as verticallines in the image, in the two dimensional plane the marker 2215 appearsto be located between the lines formed by markers 2230, 2235, 2240. Eachof the markers 2230, 2235, 2240 corresponds to an angle such thatidentifying the angle using the component selection instrument enablesthe physician to select an implant, such as a caudad facet joint, havingan angled orientation that best matches the anatomy of the patient. Asshown in FIG. 21 the image depicted has two component selectioninstruments 2201, 2201′. The first component selection instrument 2201has marker 2215 between two markers positioned nearest the midline ofthe spine. The marker nearest the midline of the spine corresponds to a30° angle, thus the facet joint selected for the joint measured bycomponent selection instrument 2201 is a 30° facet joint device. Thesecond component selection instrument 2201′ has marker 2215 positionedpartially over the middle vertical marker. The middle vertical markercorresponds to a 20° angle, thus the facet joint selected for the jointmeasured by component selection instrument 2201′ is a 20° facet jointdevice.

FIG. 22 illustrates another image of a vertebral body from a side view2300. The spinous process 22 is apparent as well as the superior facetjoint 32. In viewing the corresponding radiographic image from the sideof a spine having a two component selector instruments associatedtherewith along with the template, the image indicates that the sizecomponent would correspond to 11°. The ball marker 2315 appears as aball near the spine 12 in the image. In the component selectioninstrument 2301 of this device, two different types of markers have beenused as described above, smooth profiled wire, and turned wire with acurved profile. The first marker 2311 of the first component selectioninstrument is a smooth wire, the second marker 2311′ of the secondcomponent selection instrument is a turned marker. Thus enabling thephysician to associate two component selection instruments within thespine and to determine, based on the type of marker 2311, 2311′ thelocation of within the spine that corresponds to the measurement. Whenmeasuring the sagittal plane angles using an image taken from thisorientation, a template is lined up with the posterior wire 2320 and thedistal face of the head 2310 at an axis 2313. On the opposing side ofthe axis 2313 a series of lines can be measured to correspond to theappropriate angle of the device to be implanted. Three angle lines aredepicted, +1, +6, +11. In selecting the angle, the line that correspondsto the top surface of the vertebral body associated with the componentselection instrument is selected. In the image provided, the selectioncorresponds to the +11.

If desired, the implantable spinal components can be selected from agroup of modular components having dimensions and sizes which directlycorrespond to the various measurements determined from the componentselection instrument (or can be marked with similar markings on thecomponent and component selection/template). For example, the verticalradiopaque markers on the component selection instrument could be marked10°, 20° and 30° (which would desirably be visible on the radiographicimage), and similar markings (10°, 20° and 30°) could appear on thecorresponding modular components (in this embodiment, the modular stems)of the artificial facet joints. Similarly, the template couldincorporate markings for −4°, −9°, 1°, 6° and 11°, and similar markings(−4°, −9°, 1°, 6° and 11°) could appear on the corresponding modularcomponents (in this embodiment, the modular caudad cups) of theartificial facet joints.

In a similar manner, a single lateral image can desirably be utilized todetermine the necessary characteristics of the targeted vertebralbody(ies) as well. For a lateral view, the component selectioninstrument incorporates a single horizontal marker, which can be seen onthe radiographic image. Desirably, a clear or translucent template, suchas described above with respect to FIG. 22, can be placed over theradiographic image (or against the monitor screen, in the case ofreal-time fluoroscopy), and the angle between the upper endplate (orother desired anatomical feature) and the marker can be assessedvisually with the template. Desirably, the physician can then choose theimplant component which corresponds to that measurement. As with thepreviously described views, in a desired embodiment, a single lateralview can be utilized to characterize the pedicle of a single targetedvertebral body. In a more desirable embodiment, a single lateral viewcan be utilized to characterize both pedicles of a single targetedvertebral body, each pedicle of which will incorporate a singlecomponent selection instrument. In a most desirable embodiment, a singlelateral view can be utilized to characterize the pedicles of multipletargeted vertebral bodies (adjacent or non-adjacent), with the pediclesof the vertebral bodies each incorporating a single component selectioninstrument.

Desirably, the component selector instrument(s) will, when properlypositioned, allow the physician to take a single lateral radiographicimage, and/or a single anterior/posterior (A/P) image, and determine thenecessary characteristics of the targeted vertebral body(ies) toaccurately choose components and construct a facet replacement constructwith minimal time, effort and radiation exposure to the patient.Moreover, because in various embodiments the entirety of the componentselection instrument is contained within the wound, and desirably doesnot extend out of the wound opening, the disclosed measurement systemsignificantly reduces the opportunity for the radiographic imagingapparatus to contact objects in the sterile field. If desired, one ormore component selection instruments could be implanted, and then thesurgical wound covered and/or closed, and imaging to occur, with noreduction in the ability of the apparatus to measure the anatomicalcharacteristics of the surgical site. In addition, because the disclosedanatomical measurement system determines the anatomical measurementsthrough comparisons of angular relationships and/or known distances, thedisclosed system is desirably immune to the effects of magnificationand/or distortion of the radiographic images (which can include unknownmagnification of the radiographic images, varying monitor and/orprint-out size, and/or inaccurate and/or out-of-date calibration of theimaging equipment itself).

In use, a physician can perform a surgical procedure (including surgicalprocedures that result in destabilization and/or damage to the spinalcolumn and/or facet joints), and then prepare the surgical site forimplantation of a facet joint replacement device. Desirably, the surgeonwill drill a hole into each pedicle of the targeted vertebral body(ies),and then insert a component selection instrument into the hole. Toreduce the size and “footprint” of the component selection instrument,each component selection instrument desirably incorporates areduced-width gripping section, which facilitates gripping andmanipulation of the component selection instrument using a pair ofsurgical clamps or forceps, but allows the clamp to be removed duringvisualization, if desired, (as well as to reduce the size and“footprint” of the component selection instrument within the wound).Desirably, the surgeon will visually align the component selectioninstrument (using, for example, the lateral edge of the body, etc.) withthe spinous process of the targeted vertebral body, or other desiredanatomical landmark. One the radiographic images (A/P and lateral) havebeen taken, the component selection instruments can be removed andimplantation of the desired facet joint replacement components can beaccomplished.

With respect to the measurement and characterization of the cephaladcomponents for a facet joint replacement artificial facet joints, asimilar component selection instrument can be utilized. However, becausethe cephalad components can be significantly different in form and/orfunction from the caudad components, a component selection instrumentbest suited for measurement and characterization of cephalad componentsmay measure significantly different anatomical characteristics of thecephalad and/or caudad vertebral bodies.

The radiolucent tool with radiopaque markers allows a surgeon todetermine which angles are appropriate for the artificial orthopedicdevices being inserted, such as the artificial caudad facet joint andthe artificial cephalad facet joint described above. By using imagingand referencing the integral radiopaque marker in the instrument againstanatomical references of a patient, the surgeon can determine theappropriate angle of device to use to achieve optimal results for thepatient. The device can also be adjusted in situ to reference anatomicallandmarks through direct visual means, or to allow the user to determinethe most appropriate angle for viewing.

FIG. 23 illustrates a flow chart of a method for using the componentselection tool. Initially, target anatomy is accessed, preferably in aminimally invasive fashion. A pilot hole is drilled 2400, e.g. in thetarget vertebral body. The stem of the component selection instrument isthen inserted into the pilot hole 2402. Where the component selectiontool has is stepped or telescoped, or has a variable diameter along itslength,.the depth to which the component selection tool may be insertedinto the pilot hole may be effected, as discussed above. The depth atwhich the component selection tool is inserted can be adjusted 2404, ifdesired. Once sufficient depth is obtained 2406, a radiologic image istaken of the patient 2408 using known techniques. The image is thenanalyzed 2410 to determine the location of the markers in the componentselection instrument relative to the target anatomy. At any point, thepilot hole can be revised 2411 to provide a pilot hole with a largerdiameter after which another image can be taken (thus repeating step2408). Based on one or more images taken, a suitable artificial jointcan be selected 2412 for the target anatomy.

While preferred embodiments of the invention have been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.Moreover, while the present inventions have been described for use witha modular artificial joint system, it should be understood that thepresent inventions have utility in conjunction with the measurement andplacement of other artificial joint systems, including single component,multi-component and custom-made artificial joints, with varying results.Further, the trialing system described herein can comprise single ormulti-component tools and devices.

1. A component selection tool adapted and configured for use in a spinalcolumn comprising: a stem adapted to be inserted into a pedicle of avertebral body, the stem comprising a first marker having a first twodimensional geometric profile; and a head extending from the stem, thehead comprising a plurality of second markers, the plurality of secondmarkers each having a second two-dimensional geometric profile differentfrom the first two-dimensional profile.
 2. The component selection toolof claim 1 wherein the stem and the head are integrally formed.
 3. Thecomponent selection tool of claim 1 wherein the stem is adapted andconfigured to engage the head.
 4. The component selection tool of claim1 wherein at least one of the stem and the head are formed fromradiolucent material.
 5. The component selection tool of claim 1 whereinthe first marker is a radiopaque ball.
 6. The component selection toolof claim 1 wherein the second radiopaque markers are each a cylindricalrod or tube with a shaped exterior surface.
 7. The component selectiontool of claim 1 wherein at least one of the second radiopaque markershas an exterior shape selected from smooth, turned and notched.
 8. Thecomponent selection tool of claim 1 wherein the plurality of secondradiopaque markers each have an exterior shape that is one of smooth,turned or notched.
 9. The component selection tool of claim 1 whereinthe plurality of second radiopaque markers have at least one firstexterior shape that is smooth, turned or notched, and a second exteriorshape different from the first exterior shape.
 10. The componentselection tool of claim 1 wherein the plurality of second radiopaquemarkers lie in a single plane within the head.
 11. The componentselection tool of claim 1 wherein the plurality of second radiopaquemarkers are positioned parallel in a plane.
 12. The component selectiontool of claim 1 wherein the head further comprises a plurality of thirdradiopaque markers.
 13. The component selection tool of claim 12 whereinthe third radiopaque markers are positioned perpendicular in a plane tothe second radiopaque markers.
 14. The component selection tool of claim12 wherein the plurality of third radiopaque markers have an exteriorshape selected from smooth, turned and notched.
 15. The componentselection tool of claim 12 wherein the plurality of third radiopaquemarkers each have an exterior shape that is one of smooth, turned ornotched.
 16. The component selection tool of claim 12 wherein theplurality of third radiopaque markers have at least one first exteriorshape that is smooth, turned or notched, and a second exterior shapedifferent from the first exterior shape.
 17. The component selectiontool of claim 12 wherein the plurality of third radiopaque markers liein a single plane within the component selection tool.
 18. The componentselection tool of claim 12 wherein the plurality of third radiopaquemarkers are positioned non-parallel in a plane.
 19. The componentselection tool of claim 1 wherein the stem has a cylindrical shape witha first diameter at a distal end and a second diameter at a proximalend.
 20. The component selection tool of claim 1 wherein the stem istelescoping.
 21. The component selection tool of claim 1 wherein thestem has a diameter of 6.5 mm or less.
 22. The component selection toolof claim 1 wherein the stem has a diameter between 4.5 mm and 6.5 mm.23. The component selection tool of claim 1 wherein the stem defines alongitudinal axis, the first marker being disposed along thelongitudinal axis, at least one of the second markers being spaced awayfrom the longitudinal axis.
 24. The component selection tool of claim 1wherein the head has a dimension at least twice a diameter of the stem.25. The component selection tool of claim 24 wherein the head dimensionis parallel to the stem diameter.